JP5466482B2 - Digital conversion device and power conversion device - Google Patents

Description

  The present invention relates to a digital conversion device that converts an analog signal (for example, an information signal indicating a current value that changes from time to time) into a digital signal, and a power configuration using the digital conversion device and switching means. The present invention relates to a power conversion device for so-called power electronics that performs conversion according to the purpose of use. In particular, the present invention relates to a power converter that once converts AC power into DC and then converts it into another AC, and a power converter that converts DC power into a plurality of completely separate AC power. Specific examples of the power converter include home and business use air conditioners and refrigerators that use an AC power source to drive an electric compressor with an inverter at a variable speed.

  Some power converters include both a converter unit that converts AC power into DC power and an inverter unit that converts DC power into arbitrary AC power. In order to control these and supply desired power to a load (for example, a motor), the converter unit and the inverter unit usually detect current values and voltage values, and based on the detected values, the converter unit and The inverter unit is controlled.

  Conventional power converters either separately implement a control circuit that controls the converter unit and the inverter unit, or sensing information used for control is obtained in a state insulated from the power system. In particular, with respect to sensing of input or output current, it is common to use a current sensor that uses the Hall effect so that instantaneous current can be sensed while being insulated from the power system (for example, Patent Documents). 1). However, this configuration requires a current sensor due to the Hall effect. The more accurate current sensor based on the Hall effect is relatively expensive.

  On the other hand, instead of a current sensor, a power converter that obtains current sensing information by inserting a low resistance into a system in which current is to be sensed and sensing the potential at both ends thereof is also well known (resistor 112 in FIG. 1). 113). In this case, if one end of the control circuit and the capacitor is set to a common potential, the potential at one end of one resistor becomes a value proportional to the converter current, and the potential at one end of the other resistor becomes a value proportional to the inverter current. Using these values, it is possible to realize converter control, which is power supply current control, and inverter control, which is motor drive control. However, in an actual circuit, it is difficult to completely match the potential at one end of the capacitor, the potential at one end of the two resistors, and the reference potential of the control circuit. In addition, the circuit of the power conversion device has an inductance component other than the resistance component, and a voltage proportional to the instantaneous current cannot always be generated. In particular, in power electronics, power conversion is performed while switching the path by switching. Therefore, there is a place where current flows intermittently in the circuit, and a large voltage is instantaneously generated due to the inductance component, resulting in noise. In order to reduce this noise, it is necessary to reduce the inductance component, and methods such as making the wiring thicker and shorter are taken, but actual parts have a certain size, and there is a limit to shortening it . Therefore, the two pieces of information on the converter side and the inverter side interfere with each other. Specifically, pulse-like noise is superimposed on the detected voltage on the converter side at the timing when the voltage of the resistor on the inverter side changes greatly (see FIG. 3A), and the detected voltage on the inverter side The pulse-like noise is superimposed at the timing when the IGBT is actually turned on / off (see FIG. 3B). As described above, since the pulse noise is superimposed at the changing edge of the IGBT on both the converter side and the inverter side, it is necessary to remove the pulse noise.

  For example, if the control circuit is realized by a single control circuit, all the change timings of the IGBTs used in the converter and the inverter are monitored, and the voltages of the two resistors during that period are not used as sensing information Alternatively, it is conceivable to obtain sensing information after the voltage output of the two resistors passes through the high-frequency cutoff filter. When monitoring the change timing of the IGBT and not reading the voltage information during the change period, it is necessary to know the exact change timing, but the actual change timing of the IGBT is determined by the control circuit. Since it is slightly deviated from the change timing, it is difficult and unrealistic to know the exact change timing. Similarly, when the voltage output is passed through the high-frequency cutoff filter, the read timing is shifted, so if information on multiple phases is included in a time-division manner, such as the waveform on the inverter side, another phase It is unrealistic to obtain a great effect. In particular, when a high-frequency cutoff filter is used, information delay occurs, making it difficult to achieve stable and highly accurate control. Therefore, in a power converter provided with a converter part and an inverter part, noise cannot be removed by a simple method.

  There is also a power conversion device that converts direct current power into a plurality of completely separate alternating current powers (see FIG. 9). However, even when a plurality of motors are controlled independently from a DC power source via a plurality of inverters, the current information obtained by a plurality of current detection resistors is the timing at which the currents of each other change rapidly. Pulse noise is given to the current waveform (see FIGS. 10A and 10B). Even in such a case, in order to realize stable and highly accurate control, it is necessary to remove the pulse noise. In this case, the same problem as described above occurs.

  Therefore, the conventional power conversion device includes an AD conversion unit that removes pulse noise. FIG. 11 is a circuit configuration diagram showing the principle of noise removal of an AD conversion unit of a generally well-known one-chip microcomputer. In order to realize digital control, the AD conversion unit 1000 first holds analog information at a constant analog value by passing through a sample and hold circuit (S & H) 1001 so that the value does not change during AD conversion. The AD conversion circuit (ADC) 1009 converts the held analog value into a digital value, and stores each of the storage units 1011, 1012, and 1013 as a conversion result 1, a conversion result 2, and a conversion result 3 for each conversion. Store in order. When the three conversions are completed, the discrete value removal circuit 1007 removes the farthest value, and the averaging circuit 1008 averages the remaining values. In this way, the influence of pulsed noise is removed.

  FIG. 12 shows the conversion and calculation by the AD conversion unit 1000 in time series. The AD conversion unit 1000 receives an analog information take-in & AD conversion start signal from the entire system such as an air conditioner including the power conversion device, performs the first AD conversion, and converts the result into a conversion result 1 Store and hold in When the first AD conversion is completed, the second AD conversion is performed, and the result is stored and held in the conversion result 2. When the second AD conversion is completed, the third AD conversion is performed to obtain the result. When the third AD conversion is completed, a value farthest from the three previous AD conversion results is removed, and an average result of the remaining removed values is obtained. Thereafter, this average result is adopted as the AD conversion result from which noise has been removed.

JP 2006-158155 A

  However, in the conventional AD conversion, although the pulse-like noise component is removed, the AD conversion result is obtained after the AD conversion is first started (that is, the average after receiving the acquisition & AD conversion start signal) It takes a long time to obtain the output after conversion. For this reason, there is a problem that a delay occurs in the obtained information, and it is difficult to realize stable and highly accurate control in the control circuit using the information.

  The present invention solves the above-described conventional problems, and a digital conversion device that removes a pulsed noise component without causing delay in the obtained information, and power conversion that performs power conversion using the digital conversion device An object is to provide an apparatus.

In order to solve the above problems, digital conversion device of the present invention, the information signal values in every moment changes entered respectively delayed by a predetermined time, a plurality of information holding the value when the input A signal holding unit, a plurality of conversion units for AD-converting values held in a plurality of information signal holding units and outputting digital values, and a digital value having the most distant value among the digital values output from the conversion unit A removal unit that removes the value, and an average unit that averages the digital values that have not been removed by the removal unit and outputs them as digital information. value shorter der than the time required for conversion is, and, being greater than the time width of the pulse-like noise contained in the information signal input to the plurality of information signal holding units. Since the timing of capturing information signals by the plurality of information signal holding units is shorter than the time required for conversion to digital information in the converting unit, digital information can be output in a short time. In addition, since the most distant value is removed by the removing unit, even if pulsed noise is included during a predetermined time, the noise can be removed. Therefore, it is possible to remove a pulse-like noise component without causing a delay in the obtained information. Thereby, a highly accurate control information signal can be obtained at high speed. Therefore, the control accuracy can be increased. In the above invention, since the noise removal operation is performed after digital conversion, the number of circuit elements increases. However, since each circuit element does not require a very good characteristic, it has an advantage that it can be easily realized as a large-scale integrated circuit (LSI). Further, even if the information signal is disturbed by one pulse noise by making the predetermined time larger than the time width of the pulse-like noise included in the information signals input to the plurality of information signal holding units, An information signal that is not disturbed by noise can be held either before or after the delay.

  The value of the information signal held by the plurality of information signal holding units is preferably three or more. Thereby, pulse-like noise can be more reliably removed.

  Information signals input to the plurality of information signal holding units may indicate current values. In power conversion, current information changes drastically due to changes in the path through which current flows. That is, the current information is information that most significantly represents the control state. Therefore, by capturing the change in the current information at a high speed by the digital conversion device, the power conversion device including the digital conversion device can realize highly accurate power conversion.

  The removing unit may remove the maximum value and the minimum value. Thereby, the hold value disturbed by the pulse-like noise can be easily and reliably removed.

  The power converter of the present invention includes a DC power converter that converts the output of an AC power source into DC power using a switching element, an AC power converter that converts DC power output from the DC power converter, and digital A control circuit for controlling the DC power converter and the AC power converter based on the current information, a resistor connected to each DC power part of the DC power converter and the AC power converter, and a voltage at one end of the resistor The digital conversion device that detects the DC current of the DC power conversion unit and the AC current of the AC power conversion unit by detecting the voltage at the end as a reference, and converts the detected DC current and AC current into digital current information, respectively. And having. By providing the digital conversion device, pulse-like noise can be easily removed in a short time, so that the control accuracy of power conversion can be increased with a simple circuit configuration. Moreover, since it is possible to detect the current information of the DC power converter and the AC power converter only by detecting the voltage at one end of each resistor, this can be realized with a simple circuit configuration.

  A power converter according to another aspect of the present invention includes a plurality of AC power converters that convert a DC power source or an output of a pseudo DC power source obtained by converting an AC power source into DC, and a plurality of AC power converters based on digital current information. A control circuit for controlling the AC power conversion unit, a resistor connected to each path from the DC power supply or pseudo DC power supply side to the plurality of AC power conversion units, and a voltage at one end of the resistor as a reference to the voltage at the other end And detecting the alternating current of a plurality of alternating current power converters, and converting the detected alternating current into digital current information, respectively. By providing the digital conversion device, pulse-like noise can be easily removed in a short time, so that the control accuracy of power conversion can be increased with a simple circuit configuration. In addition, since it is possible to detect current information of a plurality of AC power conversion units only by detecting the voltage at one end of each resistor, this can be realized with a simple circuit configuration. In particular, when a motor or the like is driven by an inverter, a pulsed leakage current is generated via a stray capacitance between the motor and its case (exterior part), and noise is generated in the inverter system via another motor. Since it may mix, this invention has a big effect.

  According to the present invention, digital conversion in which noise is removed in a short time by sampling and holding an information signal (for example, a signal indicating a current value) at an interval shorter than the time required for conversion into digital information. Later signals can be output. Therefore, it is possible to remove a pulse-like noise component without causing a delay in the obtained information. Thereby, stable and highly accurate power conversion control can be performed.

The circuit block diagram which shows the whole structure of the power converter device of Embodiment 1-3 of this invention Configuration diagram of AD converter in Embodiment 1 of the present invention (A) is a diagram illustrating an example in which noise is included in the voltage on the converter side, (b) is a diagram illustrating an example in which noise is included in the voltage on the inverter side. The figure which shows the operation timing of the AD conversion part shown in FIG. The figure which shows the timing of sampling of the sample hold circuit shown in FIG. Configuration diagram of AD converter in Embodiment 2 of the present invention The figure which shows the operation timing of the AD conversion part shown in FIG. Configuration diagram of AD converter in Embodiment 3 of the present invention The circuit block diagram which shows the whole structure of the power converter device of Embodiment 4 of this invention (A) is a diagram illustrating an example in which noise is included in the voltage on one inverter side, (b) is a diagram illustrating an example in which noise is included in the voltage on the other inverter side. Configuration diagram of conventional AD converter The figure which shows the operation timing of the AD conversion part of a prior art example

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
The power conversion device according to the first embodiment of the present invention includes an AD conversion unit that samples and holds a current value at an interval shorter than the time required for conversion to digital information, and noise is removed from the AD conversion unit in a short time. By acquiring the output after digital conversion, stable high-precision control is realized. The power converter of this embodiment is built in systems, such as an air conditioner, for example.

1.1 Configuration of Power Conversion Device FIG. 1 shows an overall configuration diagram of a power conversion device according to Embodiment 1 of the present invention. The power converter of this embodiment includes an active converter circuit (DC power converter) 116 that converts AC power output from the AC power supply 101 into DC power, and a rectified current output from the converter circuit 116. A smoothing capacitor 106 for smoothing, an inverter circuit (AC power converter) 107 for converting DC power obtained by smoothing by the smoothing capacitor 106 to AC power, a control circuit 109 for controlling the converter circuit 116 and the inverter circuit 107, Have

  The converter circuit 116 includes a diode bridge 102 connected to the AC power supply 101, a reactor 103 connected to one end of the diode bridge 102, a high-speed diode 105 connected to the other end of the reactor 103, a reactor 103 and a diode 105 IGBT 104 having one end connected to each other and the other end connected to a reference potential. The smoothing capacitor 106 is connected between the cathode of the diode 105 and the reference potential. The current rectified by the converter circuit 116 is smoothed by the smoothing capacitor 106, so that the output obtained from the smoothing capacitor 106 becomes a DC power source. The inverter circuit 107 is realized by a three-phase bridge circuit that converts DC power into three-phase pseudo-AC. The three-phase pseudo alternating current output from the inverter circuit 107 is supplied to the motor 108 to drive the motor 108.

  In order to detect a direct current of the converter circuit 116, a resistor 113 is connected between the other end of the diode bridge 102 and a reference potential. Similarly, in order to detect the alternating current of the inverter circuit 107, the resistor 112 is connected between the inverter circuit 107 and the reference potential. The potentials at one end of the resistors 112 and 113 and the potential at one end of the smoothing capacitor 106 are connected from the same portion as the reference potential of the control circuit 109 and become substantially the same potential. Since the control circuit 109 and one end of the smoothing capacitor 106 have substantially the same potential, the potential on the diode bridge 102 side of the resistor 113 is a value proportional to the current of the converter circuit 116. Therefore, a current proportional to the converter circuit 116 can be detected by detecting the voltage Vconv at one end of the resistor 113 with reference to the reference potential at the other end. Similarly, the potential on the inverter side 107 of the resistor 112 has a value proportional to the current of the inverter 107. Therefore, by detecting the voltage Vinv at one end of the resistor 112 with reference to the reference potential at the other end, a value proportional to the current of the inverter 107 can be detected.

  The control circuit 109 includes an AD conversion unit (digital conversion device) 151 that AD converts an input analog information signal, and a converter control unit 111 that controls the converter circuit 116 based on the output of the AD conversion unit 151. The control circuit 109 further includes an AD conversion unit (digital conversion device) 152 that performs AD conversion on the input analog information signal, and an inverter control unit 110 that controls the inverter circuit 107 based on the output of the AD conversion unit 152. Including. The control circuit 109 performs power supply current control for controlling the converter circuit 116 and motor drive control for controlling the inverter circuit 107. In the present embodiment, the control circuit 109 is realized by a digital computer.

  Specifically, the information signal input by the AD converter 151 is a current of the converter circuit 116 detected as a voltage by the resistor 113. Further, the output voltage of the diode bridge 102 and the voltage of the smoothing capacitor 106 may be input to the AD conversion unit 151. The information signal input by the AD converter 152 is a current of the inverter circuit 107 detected as a voltage by the resistor 112. Note that the voltage of the smoothing capacitor 106 may be input to the AD conversion unit 152.

  The converter control unit 111 receives the instantaneous value of the absolute value of the AC voltage and the voltage of the smoothing capacitor 106 by looking at the output voltage of the diode bridge 102 based on the output of the AD conversion unit 151, for example. To see the output voltage on the DC side. The converter control unit 111 performs switching control of the IGBT 104 so as to obtain the same current waveform as the AC voltage, and adjusts the magnitude of the input current waveform so that a desired DC voltage is obtained. Thereby, a rectifier circuit having a good power factor is realized. The inverter control unit 110 also looks at the DC-side input voltage by looking at the voltage of the smoothing capacitor 106 based on the output of the AD conversion unit 152.

  FIG. 2 shows an internal configuration of the AD conversion unit 151 and the AD conversion unit 152. Since the AD converter 151 and the AD converter 152 have the same internal configuration, an example in which the AD converter 151 converts the information signal described above into digital information will be described below with reference to FIG. The AD conversion unit 151 takes in an analog information signal, an information signal created for starting control inside the digital computer, and a signal instructing start of AD conversion (hereinafter referred to as an “operation start signal”). Enter. The AD conversion unit 151 includes three sample and hold circuits (S & H) 301, 302, and 303 that sample and hold an input information signal, and delay circuits 304, 305, and 306 that delay an operation start signal for a predetermined time.

  The sample hold circuits (information signal holding units) 301, 302, and 303 include analog switches and capacitors that hold information. An analog information signal to be converted is input to three sample and hold circuits 301, 302, and 303. The sample and hold circuit 301 samples and holds the input information signal based on an operation start signal that instructs to take in the information signal and start AD conversion. The sample hold circuit 302 samples and holds the input information signal based on the operation start signal delayed by the delay circuit 304. The sample hold circuit 303 samples and holds the input information signal based on the operation start signal delayed by the delay circuit 304 and the delay circuit 305. That is, the sample hold circuits 301, 302, and 303 respectively hold values that have elapsed in this order.

  The AD converter 151 is further removed by a discrete value removal circuit 307 that removes the farthest value from the signals output from the three sample and hold circuits (S & H) 301, 302, and 303, and a discrete value removal circuit 307. An average circuit 308 that averages the values that did not exist, and an AD conversion circuit (ADC) 309 that AD-converts the values output from the average circuit 308 are included. Based on the operation start signal delayed through the delay circuits 304, 305, and 306, the AD conversion circuit 309 starts AD conversion from a time further delayed than the time when the sample and hold circuit 303 performs sample and hold. The AD conversion result output from the AD conversion circuit 309 is used by the converter control unit 111 for controlling the digital computer.

  In the AD converters 151 and 152 of this embodiment, the predetermined time (that is, the sampling interval of the information signal of each sample and hold circuit) for which the delay circuits 304 and 305 delay the operation start signal is digital information by the AD converter circuit 309. It is set to a value shorter than the time required for conversion to.

1.2 AD Conversion Operation The noise removal operation of the AD conversion units 151 and 152 of the power conversion apparatus configured as described above will be described. FIG. 3A shows a waveform of the voltage Vconv detected by the resistor 113 on the converter side, and FIG. 3B shows a waveform of the voltage Vinv detected by the resistor 112 on the inverter side. FIG. 3A and FIG. 3B show how the two voltages on the converter side and the inverter side interfere with each other. When the power conversion device shown in FIG. 1 operates, information indicating the values of the voltages Vconv and Vinv shown in FIGS. 3A and 3B is input to the AD conversion units 151 and 152 as current information, respectively.

  The voltage Vconv on the converter side has a basic waveform that increases during a period when the IGBT 104 is ON (t1 to t3, t4 to t7) and decreases during a period when the IGBT 104 is OFF (t3 to t4, t7 to t8). Pulse-shaped noise is superimposed on this basic waveform at the timing when the inverter-side voltage Vinv changes greatly (t1, t2, t5, t6). The voltage Vinv on the inverter side changes greatly at the timing when the ON / OFF state of the IGBT in the inverter circuit (three-phase bridge circuit) 107 changes. On the other hand, in the waveform of the voltage Vinv on the inverter side, information related to the current of each phase of the motor 108 appears in a time-sharing manner, and the voltage waveform of the resistor 112 at the timing when the IGBT 104 on the converter side is actually turned on / off. Pulse noise is superimposed on (t3, t4, t7, t8).

  Thus, since the pulse noise is superimposed on the changing edge of the IGBT on both the converter side and the inverter side, the control circuit 109 needs to remove this pulse noise. Therefore, the control circuit 109 removes this pulse noise by the AD converters 151 and 152.

  FIG. 4 shows operation timings of the AD converters 151 and 152 shown in FIG. Since the AD converter 151 on the converter side and the AD converter 152 on the inverter side have the same circuit configuration, the operation timing is the same. Hereinafter, a case where the AD conversion unit 151 on the converter side AD converts the current information detected as the voltage Vconv by the resistor 113 will be described as an example. When the AD conversion unit 151 receives an operation start signal for starting analog to digital conversion from an entire system (such as an air conditioner) including the power conversion device of this embodiment, the three sample hold circuits 301 and 302 are received. , 303 operate sequentially to capture current information detected as a voltage by the resistor 113.

  FIG. 5 shows an example of sampling timing of the three sample hold circuits 301, 302, and 303. The sample hold circuits 301, 302, and 303 take in the current information Vconv at every predetermined delay time TA based on the operation start signal that has passed through the delay circuits 304 and 305 shown in FIG. The predetermined delay time TA is set to be larger than the time width of the pulsed noise included in the information signal. Also, as shown in FIG. 4, the predetermined delay time TA is set to a value shorter than the time TB required for AD conversion.

  Returning to FIG. 4, the sample hold circuits 301 and 302 hold the acquired values until the sample hold circuit 303 acquires the current information. When the information signal capturing is completed in all the three sample hold circuits 301, 302, and 303, the captured value is input to the discrete value removal circuit 307. The discrete value removal circuit 307 removes a value farthest from the three acquired sampling results. In FIG. 5, since the pulsed noise is present near the timing of the second sampling, the result of the second sample hold becomes a value that differs greatly from the others. Therefore, the discrete value removal circuit 307 removes the second sample hold value and passes only the first and third sample hold values.

  The two sample hold values that have passed through the discrete value removal circuit 307 are averaged by the averaging circuit 308, and the averaged value is sent to the AD conversion circuit 309. The AD conversion circuit 309 AD converts the averaged value.

  Thus, in order to remove the most distant value in the discrete value removal circuit 307, the signal output from the AD conversion circuit 309 is the one from which noise has been removed. This signal is sent to the converter control unit 111. Similarly, a signal from which noise has been removed by the AD conversion unit 152 is sent to the inverter control unit 110.

1.3 Summary According to the power conversion device of this embodiment, the AD converters 151 and 152 remove pulse-like noise due to inductance such as wiring included in information such as current, which is important information in power conversion. be able to. Therefore, high-accuracy information can be obtained at high speed by a simple method using resistors and the like, and the control accuracy of power conversion can be increased. Since the power conversion device according to the present embodiment can perform sensing by removing pulsed noise, high-accuracy power conversion control can be realized by a simple sensing method. Thereby, the power converter device of this embodiment is applicable also to uses, such as a domestic and business air-conditioner, a refrigerator, or a washing machine using electric power similarly. In addition, it is effective when there are a plurality of AC loads such as a motor to be controlled.

  In particular, as is apparent from the timing chart of FIG. 4, in the present embodiment, the predetermined delay time TA, which is the sampling interval, is set to a value shorter than the time TB required for conversion to digital information. Therefore, as compared with the general noise removal method shown in FIG. 12, the time TC from the input of analog information to the acquisition of final digital information is significantly shortened. Therefore, noise can be removed without causing delay in the obtained information. In addition, according to the present embodiment, AD conversion is not performed every time an analog value is captured, and AD conversion is performed after averaging processing. Therefore, the time TC until digital information is acquired can be shortened. Thereby, the power converter of this embodiment can realize stable and highly accurate control.

  In addition, according to the present embodiment, AD conversion is performed after the noise removal calculation (that is, processing is performed by a simple analog circuit portion), so that there is an advantage that the circuit can be simplified.

  As shown in FIG. 5, since the noise has a short pulse shape, there is almost no possibility that two of the three sample hold values are disturbed. Therefore, a large pulse noise can be sufficiently removed by the method of the present embodiment. Also, when the noise in the pulse state enters between the delays of three sample and hold, any sample and hold value is not disturbed, so that the removal of a large pulse noise can be realized.

  In this embodiment, the delay time TA in each sample and hold is set to be larger than the time width of the pulsed noise included in the information signal of analog input. Therefore, it is not possible to sample and hold two or more noise values. Therefore, by removing one piece of information that is farthest from the sampled and held information, the influence of noise can be sufficiently removed.

  In the present embodiment, resistors 112 and 113 are inserted at locations where current is desired to be detected, and current information is obtained from a potential difference between both ends of the resistor. Therefore, according to this embodiment, pulse-like noise can be removed by a simple detection method, and the control accuracy of power conversion can be improved. In power conversion, current information may change drastically due to changes in the path through which current flows. That is, the current information is information that most significantly represents the control state. Therefore, high-accuracy power conversion can be realized by capturing this change in information at high speed.

  In this embodiment, three sample and hold circuits are provided and the number of three analog information signals is sampled and held. However, this number is not limited to three. For example, the number of sample hold circuits and the number of sample hold values may be four or more. Since the more accurate value can be calculated as the number of information signals used for the calculation is larger, it is preferably 3 or more.

(Embodiment 2)
The power conversion device of the second embodiment is different from the power conversion device of the first embodiment in the configuration and operation of the AD conversion units 151 and 152. The AD conversion units 151 and 152 of the first embodiment perform AD conversion last. On the other hand, in the second embodiment, AD conversion is performed immediately after sample hold. That is, after each sample and hold circuit, an AD conversion circuit is provided for each, and after all is converted into digital information, discrete values are removed and averaged by digital calculation. As a result, the AD converters 151 and 152 can be easily realized as a large-scale integrated circuit (LSI). The second embodiment is the same as the first embodiment except for the configuration and operation of the AD conversion units 151 and 152.

  FIG. 6 shows a configuration of the AD conversion unit 151 according to the second embodiment of the present invention. The AD converter 152 also has the configuration shown in FIG. Hereinafter, the configuration and operation of the AD converter 151 will be described as an example. The AD conversion unit 151 includes three sample hold circuits 301, 302, and 303 that take in an information signal that is an analog input, and an AD conversion circuit 621 that converts the output results of the three sample hold circuits 301, 302, and 303 into digital information, respectively. , 622, and 623, and delay circuits 604, 605, 606, and 620 for delaying an operation start signal for instructing the timing of start of sample hold and AD conversion for a predetermined time. The sample hold circuit 302 and the AD conversion circuit 621 operate based on the operation start signal that has passed through the delay circuit 604. The sample hold circuit 303 and the AD conversion circuit 622 operate based on the operation start signal that has passed through the delay circuits 604 and 605. The AD conversion circuit 623 operates based on the operation start signal that has passed through the delay circuits 604, 605, and 606. The AD conversion unit 151 further includes a discrete value removal circuit 307 that removes the farthest value from the information signal converted into digital information, and an averaging circuit 308 that averages the values that have not been removed. The output of the average circuit 308 becomes an AD conversion result from which noise is removed.

  FIG. 7 shows the operation timing of the AD converter 151 shown in FIG. When the AD conversion unit 151 receives an operation start signal of a command for starting analog to digital conversion from an entire system such as an air conditioner including the power conversion device illustrated in FIG. 1, three sample hold circuits Reference numerals 301, 302, and 303 sequentially operate to take in analog information at that time (for example, current information detected by the resistors 112 and 113 shown in FIG. 1). The results of the three sample and hold circuits 301, 302, and 303 are immediately sent to the AD conversion circuits 621, 622, and 623. The AD conversion circuits 621, 622, and 623 convert the sample and hold results into digital information based on the operation start signals output from the delay circuits 604, 605, and 606. The results obtained when each AD conversion operation is completed are held, and three AD conversion results are obtained when the last AD conversion is completed. Thereafter, the obtained digital information is sent to the discrete value removal circuit 307. The discrete value removal circuit 307 removes the digital information having the most distant value from the acquired digital information, and sends the value that has not been removed to the averaging circuit 308. The averaging circuit 308 averages the acquired values.

  As in the first embodiment, in FIG. 7, the predetermined delay time TA (that is, the timing of sample and hold) by the delay circuits 604, 605, and 606 is required for conversion to digital information by the AD conversion circuits 621, 622, and 623. A value shorter than time TB is set. As a result, the time TC from the reception of the operation start signal to the end of AD conversion becomes shorter than the time of FIG. 12 according to a general method, as in FIG. Note that the delay time of the delay circuit 620 is set to a time required for conversion to digital information by the AD conversion circuit 623.

  According to the present embodiment, the same effect as in the first embodiment can be obtained. That is, noise can be removed in a short time, and stable and highly accurate control can be realized.

  According to the present embodiment, since discrete value removal and averaging are performed after digital conversion, the number of circuit elements increases as compared with the first embodiment. However, since each circuit element does not require a very good characteristic, it has an advantage that it can be easily realized as a large-scale integrated circuit (LSI).

(Embodiment 3)
The power conversion device according to the third embodiment is different from the power conversion devices according to the first and second embodiments in the configuration and operation of the AD conversion units 151 and 152. In the AD converters 151 and 152 of the first and second embodiments, the discrete value removal circuit 307 removes the most distant values, but in the third embodiment, the maximum value and the minimum value are removed. In the third embodiment, other configurations and operations are the same as those in the first embodiment.

  FIG. 8 shows a configuration of the AD conversion unit 151 of the present embodiment. The AD converter 152 also has the configuration shown in FIG. Hereinafter, the configuration and operation of the AD converter 151 will be described as an example. The AD converter 151 of this embodiment includes a maximum value / minimum value removal circuit 407 that removes a signal having the maximum value and a signal having the minimum value from the input signals, instead of the discrete value removal circuit 307 shown in FIG. Use.

  An operation of removing noise in the AD conversion unit 151 in the present embodiment will be described with reference to the waveforms in FIG. In the case of the waveform shown in FIG. 5, the maximum value is the second sample hold value, and the minimum value is the third sample hold value. Therefore, the maximum value / minimum value removal circuit 407 removes the second and third sample hold values and outputs the first sample hold value. Since the first sample hold value is not disturbed by pulse noise, the output of the averaging circuit 308 is a signal from which the influence of noise has been removed. In this example, since the average circuit 308 has one input value, the input and output of the average circuit 308 are the same.

  Also in the present embodiment, as in the first embodiment, the delay time TA is set to a value shorter than the time TB required for conversion to digital information by the delay circuits 304 and 305 (see FIG. 4).

  According to the present embodiment, the same effect as in the first embodiment can be obtained. That is, noise can be removed in a short time, and stable and highly accurate control can be realized.

  Note that according to the present embodiment, the number of sample and hold circuits and the number of sample and hold values are three, but this number may be four or more. When four or more sample and hold circuits are used, there are a plurality of information signals after the maximum value and the minimum value are removed, and the plurality of signals are averaged by the averaging circuit 308. Even in this case, a value from which the influence of noise is removed can be output as an AD conversion value.

  As in the second embodiment, the present embodiment can also be applied to a configuration in which the AD conversion circuits 621, 622, and 623 are provided after the sample and hold circuits 301, 302, and 303, respectively. In this case, after all values are once converted into digital information, the maximum value and the minimum value are removed by digital calculation, and an average calculation is performed on the result.

(Embodiment 4)
The power converters of Embodiments 1 to 3 convert AC power output from the AC power supply 101 and supply the converted power to the motor. On the other hand, the power converter of Embodiment 4 converts the DC power output from the DC power supply and supplies the converted power to the motor. The power conversion device according to the present embodiment includes the same AD conversion units 151 and 152 as those in any one of the first to third embodiments.

  FIG. 9 shows the configuration of the power conversion device according to the fourth embodiment of the present invention. The power conversion apparatus of this embodiment includes an inverter A 827 and an inverter B 817 that convert DC power output from the DC power supply 806 into AC power, and a control circuit 809 that controls the inverter A 827 and inverter B 817. Inverter A 827 and inverter B 817 are realized by a three-phase bridge circuit. The AC power output from the inverter A 827 and the inverter B 817 is supplied to the motors 828 and 818. Thereby, the motors 818 and 828 are controlled independently. Current detection resistors 822 and 812 are connected between the DC power supply 806 and the inverters A827 and B817, respectively. By detecting the voltages of the current detection resistors 822 and 812 of the inverter A 827 and the inverter B 817 using the negative side of the DC power supply 806 as a reference potential, the instantaneous voltage across the current detection resistors 822 and 812 can be detected. Thereby, instantaneous currents of the two motors 828 and 818 (current values of the inverters 827 and 817) can be known. The control circuit 809 receives analog information (for example, information indicating the current values of the inverter A 827 and the inverter B 817 and information indicating the voltage value of the DC power supply 806) and AD conversion units 151 and 152 that perform AD conversion, and an AD conversion unit The inverter A control unit 820 and the inverter B control unit 810 control the inverter A 827 and the inverter B 817 based on the outputs of 151 and 152, respectively. By detecting the instantaneous currents of the motors 828 and 818 using the current detection resistors 822 and 812, the inverter A control unit 820 and the inverter B control unit 810 use the current value information to set the motors 828 and 818 respectively. Can be driven with high accuracy.

  10A shows the resistance voltage Va of the current detection resistor 822 on the inverter A 827 side, and FIG. 10B shows the resistance voltage Vb of the current detection resistor 812 on the inverter B 817 side. The resistance voltage Va and the resistance voltage Vb are input to the AD converters 151 and 152 as current information, respectively. The current information obtained by the two current detection resistors 812 and 822 gives pulse-like noise to the other current waveform at the timing when the currents suddenly change as shown in FIG. Therefore, also in this embodiment, the AD converters 151 and 152 remove this pulsed noise.

  The configuration of the AD conversion units 151 and 152 of the present embodiment is the same as that of any of the AD conversion units 151 and 152 of the first to third embodiments. That is, the sampling interval (delay time) TA is set to a value shorter than the time TB required for conversion to digital information in the AD conversion circuit 309 (see FIG. 4).

  Since the configuration of the AD conversion units 151 and 152 of the present embodiment is the same as that of any one of the AD conversion units 151 and 152 of the first to third embodiments, the same effects as the first to third embodiments are achieved according to the present embodiment. Is obtained. That is, noise can be removed in a short time, and stable and highly accurate control is possible.

  Further, according to the present embodiment, a plurality of motors can be accurately driven with a simple configuration. When driving a plurality of motors using a plurality of inverters as in this embodiment, a pulsed leakage current is generated via a stray capacitance between the motor and its case (exterior part), Leakage current may be mixed as noise in the inverter system of another motor via another motor. Therefore, when driving a plurality of motors using a plurality of inverters as in this embodiment, noise removal according to this embodiment has a great effect.

  In the present embodiment, a plurality of motors are driven using a DC power supply, but a plurality of motors may be driven using an AC power supply. In this case, similarly to the configuration shown in FIG. 1, a DC power source obtained by rectifying and smoothing the output of the AC power source is used. Even in this case, the same effect as the present embodiment can be obtained.

  Although the present invention has been described with respect to particular embodiments, many other variations, modifications, and other uses will be apparent to those skilled in the art. Accordingly, the invention is not limited to the specific disclosure herein, but can be limited only by the scope of the appended claims.

  Since the digital conversion device of the present invention can remove noise in a short time, the power conversion device using this digital conversion device has the effect of realizing stable and highly accurate power conversion control, for home use and business use. It is useful for applications such as air conditioners, refrigerators, and washing machines that similarly use electric power.

101 AC power supply 102 Diode bridge 103 Reactor 104 IGBT
105 Diode 106 Smoothing capacitor 107, 817, 827 Inverter circuit 108, 818, 828 Motor 109, 809 Control circuit 110, 810, 820 Inverter control unit 111 Converter control unit 112, 113, 812, 822 Resistance 116 Converter circuit 151, 152 AD Conversion unit 301, 302, 303 Sample hold circuit 304, 305, 306, 604, 605, 606, 620 Delay circuit 307 Discrete value removal circuit 308 Average circuit 309, 621, 622, 623 AD conversion circuit 407 Maximum value / minimum value removal circuit 806 DC power supply

Claims (6)

A plurality of information signal holding units for inputting information signals whose values change from moment to moment by delaying each by a predetermined time, and holding values when inputted,
A plurality of conversion units for AD-converting values held in the plurality of information signal holding units and outputting digital values;
A removal unit for removing a digital value having the most distant value among the digital values output from the conversion unit;
An average unit that averages digital values that have not been removed by the removal unit and outputs the digital values, and
Have
The predetermined time is a value shorter than the time required for individual conversion into digital values in the plurality of conversion units, and is in the form of pulses in the information signals input to the plurality of information signal holding units. A digital converter characterized by being larger than the time width of noise.   The digital conversion apparatus according to claim 1, wherein the number of information signals held by the plurality of information signal holding units is three or more.   The digital conversion device according to claim 1, wherein information signals input to the plurality of information signal holding units indicate current values.   The digital conversion apparatus according to claim 1, wherein the removing unit removes a maximum value and a minimum value. A direct current power converter that converts the output of the alternating current power source into direct current power using a switching element;
An AC power converter that converts DC power output from the DC power converter into AC power;
Based on digital current information, a control circuit for controlling the DC power converter and the AC power converter;
A resistor connected to each DC power portion of the DC power converter and the AC power converter;
By detecting the voltage at one end of the resistor with reference to the voltage at the other end, the DC current of the DC power converter and the AC current of the AC power converter are detected, respectively, and the detected DC current and AC current are respectively detected. The digital conversion device according to claim 1, which converts the digital current information.
A power conversion device. A plurality of AC power converters for converting the output of the DC power source or the pseudo DC power source obtained by converting the AC power source into DC, into a plurality of AC powers;
A control circuit for controlling the plurality of AC power converters based on digital current information;
Resistors connected to respective paths from the DC power supply or the pseudo DC power supply side to the plurality of AC power conversion units;
The AC current of the plurality of AC power conversion units is detected by detecting the voltage at one end of the resistor with the voltage at the other end as a reference, and each detected AC current is converted into the digital current information. A digital conversion device as described in
A power conversion device.

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